PHP Syntax Data Types, Variables, Operators, Expressions, Conditional Statements SoftUni Team Technical Trainers Software University

2 1.Data Types in PHP  Integer, Floating-Point, Boolean, String 2.Declaring and Using Variables 3.Operators, Expressions, Statements 4.Conditional Statements  If-else, switch-case 5.False-like Conditions 6.Accessing Forms Fields Table of Contents

PHP Introduction

4  PHP (PHP Hypertext Preprocessor) is server-side scripting language used for creating dynamic web content  First introduced in 1995 as module for Apache  Free and open-source, written in C  Can be deployed on almost any operating system  Provides interaction with Databases (CRUDs)  Can be embedded in HTML What is PHP?

5 PHP – Example My first PHP code! My first PHP code! <?php $myName = 'Yordan'; $myName = 'Yordan'; echo 'My name is '. $myName; echo 'My name is '. $myName; ?> ?> Code is enclosed with Code is enclosed with tags

Mixing PHP and HTML  PHP is designed to mix HTML and PHP code:  This is similar to writing echo "Hello John!";  Very useful for long texts Hello John! Hello John! You are not John. You are not John.

Data Types in PHP

8  A data type:  Is a domain of values of similar characteristics  Defines the type of information stored in the computer memory (in a variable)  PHP supports eight types:  Scalar: Boolean, Integer, Floating point, String  Compound: Array, Object  resource and NULL  PHP is a "type-less" language What Is a Data Type?

9  PHP is a typeless language  The variable types are not explicitly defined  The type of a variable can be changed at runtime  Variables in PHP are declared with the symbol $ PHP Data Types $count = 5; // variable holds an integer value $count = 'hello'; // the same variable now holds a string $name = 'Svetlin Nakov'; // variable holds a string $mark = 5.25; // mark holds a floating-point number

10  Integer types represent whole numbers  The size of an integer is platform-dependent  32-bit: to  64-bit: to  In Windows it is always 32-bit  Too large values for integer type are automatically turned into a floating-point number Integer Numbers $maxInteger = ; $maxInteger = ; echo gettype($maxInteger); // integer $maxInteger += 1; echo gettype($maxInteger); // double

11  Floating-point types represent real numbers, e.g  In PHP the floating-point numbers are 64-bit  Stored in the IEEE format  Have range from -1.79e+308 to 1.79e+308  Have precision of 15 digits  Can behave abnormally in the calculations  E.g = Floating-Point Numbers

 Convert floating-point to integer number  Convert to integer number with rounding  Convert string to integer Numbers Conversion $variable = 5; $floatVar = floatval($variable); // Or: // Or: $floatVar = (float)$variable; $floatVar = (float)$variable; $variable = ; $varInt = intval($variable); // Or: $varInt = (int)$variable; $num = "3.14"; $int = (int)$num; $float = (float)$num;

13  Has two possible values: true and false  Values are case-insensitive (True, true, TRUE & False, false, FALSE)  Is useful in logical expressions  Returns "1" or "null"  Example of Boolean variables: The Boolean Data Type echo(true); // 1 echo(false); // (nothing) var_dump(true); // bool(true) var_dump(false); // bool(false)

14  The string data type represents a sequence of characters  Strings are enclosed in quotes:  Both ' and " work correctly, with “anomalies”  Best practices suggest using single quotes  Strings can be concatenated (joined together)  Using the. (dot) operator The String Data Type $string = 'Welcome to PHP'; $name = 'Soft'. ' '. 'Uni';

 Single-quoted strings do not interpolate variables:  Double-quoted string interpolate variables:  Curly braces ensures the correct variable is interpolated Variable Interpolation $name = 'Fred'; echo 'Hello, $name'; // Hello, $name $who = 'Svetlin'; $where = 'here'; echo "$who was $where"; // Svetlin was here $n = 12; echo "You are the {$n}th person";

16  An array holds a group of values, which you can identify by position or identifying name  Arrays with number identifiers (with zero being the first position)  Associative arrays with string identifiers Array Type $students[0] = "Dean"; $students[1] = "Vladislav"; $students = array("Dean", "Vladislav"); $students['Dean'] = 6; $students['Vladislav'] = 5; $students = array('Dean' => 6, 'Vladislav' => 5);

17  A class is a definition of a structure  Contains properties (variables) and methods (functions)  Once a class is defined, any number of objects can be made from it with the new keyword  Object’s properties/methods can be accessed with the -> construct Object Type $svetlin = new Person; $svetlin->name('Svetlin'); echo "Hello, {$svetlin->name}\n"; class Person { public $name; public $name; function name ($newname) { function name ($newname) { $this->name = $newname; $this->name = $newname; }}

18  Special variable, holding a reference to an external resource  E.g. opened file, database connection, image canvas area  Resources are created and used by special functions.  Resource with no more references to it is detected automatically  It is freed by the garbage collector  is_resource() function checks whether a value is a resource Resource Type $res = database_connect(); // database connect function database_query($res); $res = "boo"; // database connection automatically closed because $res is redefined

Null Values What is NULL in PHP?

 In PHP there is a special value NULL  Undefined means that a variable is declared but not initialized  Null means that an object exists and is empty (has no value)  All variables can be reset to null with unset() Null Value <?php $variable; // variable is undefined $variable = 4; // variable has value 4 $variable = NULL; // variable has no value unset($variable); // unset($variable); // variable is undefined?>

 The variable type can be checked with gettype()  Or just print it with var_dump()  Great for checking the type and value of a given variable in the code Checking the Type of a Variable $boolVariable = true; gettype($boolVariable); // boolean $intVariable = 123; gettype($intVariable); // integer $stringVariable = "SoftUni"; gettype($stringVariable); // string $b = true; var_dump($b); // boolean(true) $i = 123; var_dump($i); // integer(123) $s = "PHP"; var_dump($s); // string("PHP")

Data Types in PHP Live Demo

Declaring and Using Variables p q i

24  A variable is a:  Placeholder of information that can be changed at run-time  A piece of computer memory holding some value  Variables allow you to:  Store information  Retrieve the stored information  Change the stored information What Is a Variable? p q i

25  A variable has:  Name  Type (of stored data)  Value  Example:  Name: $counter  Type: integer  Value: 5 Variable Characteristics $counter = 5;

26  When declaring a variable we:  Specify its name (called identifier)  The type is inferred by the value  Give it an initial value  Examples: Declaring Variables $height = 200; $str = 'Hello'; $isPositive = true;

27  Identifiers may consist of:  Letters, digits [0-9], underscore '_'  Cannot start with a digit  Cannot be a PHP keyword  Identifiers in PHP are case-sensitive  Identifiers should have a descriptive name  Only Latin letters  Variables and functions names: use camelCase Identifiers

28  Examples of correct identifiers:  Examples of incorrect identifiers: Identifiers – Examples $2Pac = 2; // Cannot begin with a digit function new() { return 5; } // new is a keyword $New = 2; // Here N is capital, so it's not a PHP keyword $_2Pac = 2; // This identifier begins with _ $поздрав = 'Hello'; // Unicode symbols used $greeting = 'Hello'; // This is more appropriate $n = 100; // Undescriptive $number_of_clients = 100; // Descriptive // Overdescriptive identifier: $numberOfPrivateClientOfTheFirm = 100;

29  The = operator is used to assign a value to a variable: Assigning Values // Assign a value (literal) to a variable $firstValue = 5; // Using an already declared variable: $secondValue = $firstValue; // Cascading assignment $thirdValue = $newValue = 3;

30  Reference the value of a variable whose name is stored in another variable by prefacing the variable reference  After the second statement executes, the variable $first has the value " second " Variable Variables // variable variables example $variable = "first"; $$variable = "second"; echo $variable; // first echo $first // second echo $$variable // second

31  References are how you create variable aliases  Variable References $firstName = "Nakov"; $secondName =& firstName; $secondName = "Karamfilov"; echo $firstName; // Karamfilov echo $secondName; // Karamfilov

32  A variable in PHP can be:  undefined  NULL  Local  Example: In this code secondVar is undefined: Variables in PHP echo($asfd); // Error $p = null; echo($p); // nothing is printed $localVar = 5; ($localVar); // 5 $localVar = 5; echo($localVar); // 5 $firstVar = 10; echo($firstVar); // 10 echo($secondVar); // Undefined variable: secondVar

Variable Scope Local, Global, Static

34  Local scope: a variable declared in a function is local to that function  Visible only to code in that function  Not accessible outside of the function  Variables defined outside a function (called global variables) are not accessible inside the function Local Scope function updateCounter() { $counter++; $counter++;} $counter = 10; updateCounter(); echo $counter; // 10

35  Variables declared outside a function are global  Can be accessed from any part of the program  Use the global keyword inside the function to access global variables  Cumbersome way to update the global variable is to use PHP’s $GLOBALS : $GLOBALS[counter] Global Scope function updateCounter() { global $counter; global $counter; $counter++; // or $GLOBALS[counter]++; $counter++; // or $GLOBALS[counter]++;} $counter = 10; updateCounter(); echo $counter; // 11

36  Static variables retain their values between calls to a function  Visible only within the function where defined  Declare a variable static with the static keyword Static Variables function updateCounter() { static $counter = 0; static $counter = 0; $counter++; $counter++; echo "Static counter: {$counter}\n"; echo "Static counter: {$counter}\n";} $counter = 10; updateCounter();updateCounter(); echo "Global counter: {$counter}\n"; Output: Static counter: 1 Static counter: 2 Global counter: 10

PHP Constants  In PHP constants are defined with the define function  Constant values cannot be changed  Doesn't start with $  Can hold any scalar value

Operators in PHP Arithmetic, Logical, Comparison, Assignment, …

39  Operator is an operation performed over data at runtime  Takes one or more arguments (operands)  Produces a new value  Operators have precedence  Precedence defines which will be evaluated first  Operators are used to build expressions  Expressions are sequences of operators and operands that are evaluated to a single value What is an Operator?

40 CategoryOperators Arithmetic + - * / % Logical && || ^ ! Binary & | ^ ~ > Comparison == != = === !== Assignment = += -= *= /= %= &= |= ^= >= String concatenation + Other. [] () ?: new Categories of Operators in PHP

41 PrecedenceOperators Highest () (postfix) new typeof (prefix) + - (unary) ! * / % + - > > = = == != Lower & Operators Precedence

42 PrecedenceOperators Higher ^ | && || ?: Lowest = *= /= %= += -= >= &= ^= |= Operators Precedence (2)  Parenthesis operator always has the highest precedence  Note: prefer using parentheses, even when it seems stupid to do so

43  Arithmetic operators +, -, *, / are the same as in math  The division operator / returns number  Division / 0 returns false and "Division by zero" warning  Remainder operator % returns the remainder from division  E.g. 5 % 3  2  The operator ++ / -- increments / decrement a variable  Prefix ++ vs. postfix ++ Arithmetic Operators

44  Logical operators take boolean operands and return boolean result  Operator ! turns true to false and false to true  Behavior of the operators &&, || and ^ (1 == true, 0 == false): Logical Operators Operation||||||||&&&&&&&&^^^^ Operand Operand Result

45  Bitwise operators in PHP always work for 32-bit integers  Bitwise operator ~ turns all 0 to 1 and all 1 to 0  Like ! for boolean expressions but works bit by bit  The operators |, & and ^ behave like bitwise ||, && and ^  The > move the bits (left or right)  Behavior of the operators |, & and ^: Bitwise Operators Operation||||&&&&^^^^ Operand Operand Result

46  Comparison operators are used to compare variables  ==,, >=, <=, !=, ===, !==  The == means "equal after type conversion"  The === means "equal and of the same type" Comparison Operators $a = 5; $b = 4; var_dump($a >= $b); // bool(true) var_dump($a != $b); // bool(true) var_dump($a == $b); // bool(false) var_dump($a == "5"); // bool(true) var_dump($a === "5"); // bool(false)

47  Assignment operators are used to assign a value to a variable  =, +=, -=, |=,...  Assignment operators examples: Assignment Operators $x = 6; $y = 4; echo($y *= 2); // 8 $z = $y = 3; // $y = 3; $z = 3; echo($z); // 3 echo($x |= 1); // 7 echo($x += 3); // 10 echo($x /= 2); // 5

48  String concatenation operator. is used to concatenate strings  If the second operand is not a string, it is converted to string automatically  Member access operator -> is used to access object members  Square brackets [] are used with arrays to access element by index  Parentheses () are used to override the default operator precedence Other Operators $output = "The number is : "; $number = 5; echo($output. $number); // The number is : 5

49  Conditional operator ?: has the form:  If b is true then the result is x, else the result is y  Also called ternary operator  The new operator is used to create new objects  this operator references the current context Other Operators (2) $b ? $x : $y

50 Other Operators (3) $a = 6; $b = 4; echo($a > $b ? "a > b" : "b >= a"); // a > b echo "SoftUni" == "SoftUni" ? "Equal" : "Not Equal"; $c = $b = 3; // b = 3; followed by c = 3; echo($c); // 3 echo(($a + $b) / 2); // 4.5 echo(gettype($a)); // integer echo(gettype([])); // array

Operators in PHP Live Demo

Expressions

53  Expressions are:  Sequences of operators, literals and variables that are evaluated to some value  Examples: Expressions $r = ( ) / 2 + 5; // r = 70 // Expression for calculation of circle area $surface = pi() * $r * $r; // Expression for calculation of circle perimeter $perimeter = 2 * pi() * $r;

If and If-else Implementing Conditional Logic

55  PHP implements the classical if / if-else statements: Conditional Statements: if-else $number = 5; if ($number % 2 == 0) { echo("This number is even."); echo("This number is even.");} else { echo("This number is odd."); echo("This number is odd.");}

56 Alternative If Syntax <?php $a == 5; $a == 5; if ($a == 5): if ($a == 5): echo "a equals 5"; echo "a equals 5"; echo "..."; echo "..."; elseif ($a == 6): elseif ($a == 6): echo "a equals 6"; echo "a equals 6"; echo "!!!"; echo "!!!"; else: else: echo "a is neither 5 nor 6"; echo "a is neither 5 nor 6"; endif; endif;?>  PHP offers an alternative syntax for the if-statement:

if and if-else Live Demo

switch-case Making Several Comparisons at Once

59  Selects for execution a statement from a list depending on the value of the switch expression The switch-case Statement switch ($day) { case 1: echo('Monday'); break; case 2: echo('Tuesday'); break; case 3: echo('Wednesday'); break; case 4: echo('Thursday'); break; case 5: echo('Friday'); break; case 6: echo('Saturday'); break; case 7: echo('Sunday'); break; default: echo('Error!'); break; }

60 1.The expression is evaluated 2.When one of the constants specified in a case label is equal to the expression:  The statement that corresponds to that case is executed 3.If no case is equal to the expression:  If there is default case, it is executed  Otherwise the control is transferred to the end point of the switch statement 4.The break statement exits the switch-case statement How switch-case Works?

61 Alternative Switch Syntax $variable = 2; switch ($variable): case 1: case 1: echo " News "; echo " News "; break; break; case 2: case 2: echo " Forum "; echo " Forum "; break; break;endswitch;  PHP offers an alternative syntax for switch constructs:

The switch-case Statement Live Demo

Accessing Form Fields from PHP Reading and Writing Form Data

64  You can access the form fields by their name property  HMTL:  PHP: Accessing Forms Fields Name: Name: </form> Welcome Welcome Your is: Your is:

Accessing Form Fields Live Demo

66  PHP dynamic data types  number, string, boolean, null, array, object  Operators are similar to C#, Java and C++  Expressions are as in C#, Java and C++  If-else statements are as in C#, Java and C++  Alternative syntax: if-elseif-endif  Switch-case statement are similar to Java / C#  Form fields can be accessed by $_GET['key'] and $_POST['key'] Summary

? ? ? ? ? ? ? ? ? PHP Syntax

License  This course (slides, examples, demos, videos, homework, etc.) is licensed under the "Creative Commons Attribution- NonCommercial-ShareAlike 4.0 International" licenseCreative Commons Attribution- NonCommercial-ShareAlike 4.0 International 68

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